Category

Published on

15 Apr 2004

Abstract

In the past few years, tremendous progress in the growth of carbon
nanotubes (CNTs) has been made, which enabled the fabrication of
various CNT devices for applications in electronics, biomedical
techniques, and chemical/biological sensors. We have established a
process to grow vertically aligned multi-walled CNTs (MWCNTs) using
DC-biased plasma enhanced chemical vapor deposition (PECVD). These
MWCNTs have been integrated, using a bottom-up approach, for (1) CNT
interconnects and (2) nanoelectrode arrays for ultrasensitive DNA
detection, both of which rely on MWCNT arrays embedded in SiO2 with
detection, both of which rely on MWCNT arrays embedded in SiO2 with
only the very end exposed at the surface of SiO2 matrix.

By depositing patterned metal contacts at the top surface, the
embedded MWCNTs can serve as vertical interconnects in integrated
circuits. The processing is fundamentally different from current Cu
damascene techniques, which avoids problems associated with etching
and filling of high aspect ratio nanoscale holes/trenches. The
MWCNTs have demonstrated an extremely high current carrying
capability, meeting the long-term requirements by International
Semiconductor Technology Roadmap (ISTR).

The embedded MWCNT array can be used as a nanoelectrode array for
developing electrochemical sensors. The temporal resolution and
sensitivity can be dramatically improved. The low-density
nanoelectrode array (<1x108 electrode/cm2) has demonstrated an
extremely low detection limit down to ~ 1 nM for redox species in the
solution. By functionalizing the MWCNT end with oligonucleotide
probes, it can be used for detecting the hybridization of specific
DNA targets through a mediator amplified guanine oxidation mechanism.
The detection of both oligonucleotide targets and PCR amplicons has
been demonstrated with a detection limit less than ~1000 molecules.
Since the inherent guanine bases in the target DNA are used as signal
moieties, this technique is label-free and can be used for rapid
molecular analyses.

Bio

Dr. Jun Li is a physical scientist with NASA at Ames Research
Center's Nanotechnology Center. His current research interests focus
on the development of new methods to integrate the nanostructured
materials to micro- and macro- sized devices in which the unique
properties of individual nanoelements are utilized to improve the
performance. The approach is to combine the
lithographic/nonlithographic patterning, self-assembly, catalytic
growth, semiconductor processing techniques, and chemical
functionalization to build individual nanoelements such as carbon
nanotubes (CNTs) and semiconducting nanowires (SNWs) into large-scale
integrated devices. Currently he is working on CNT nanoelectrode
arrays targeting at the development of ultrasensitive biosensors and
the exploration of carbon nanotubes for integrate circuit
interconnects.

Dr. Li received BS degree in chemistry from Wuhan University (P.R.
China) in 1987, MS and PhD degree in chemistry from Princeton
University in 1991 and 1995, respectively. From 1994 to 1997, he
held a postdoctoral research associate position in Chemistry
Department of Cornell University. He worked for Molecular Imaging
Co. from 1997 to 1998 and the Institute of Materials Research and
Engineering in Singapore from 1998 to 2000. He joined NASA Ames
Research Center in 2000.